Pneumatic tire



Julie 25, 1935. 5 EwART ET AL 2,006,197

PNEUMATIC TIRE Filed Oct, 1934 F f 6 INVENTORS 5 Z [ll/07f J. [IVA 7'7 Patented June 25, 1935 4 UNITED'STATES PATENT OFFlCE 2,008,197 I PNEUMATIC mm Elliott S. Ewart, St. Clair Shores, and Arthur W. Bull, Grosse Pointe, Mich, minors to United States Rubber Company, New York, N. Y., a corporation of New Jersey Applicatiofflctober 5, 1934, Serial No. 746,996

8 Claims. (01. 152-14) Our invention relates to pneumatic tires, and etc., or A--ABB-C-C-B-B--A--ACC more particularly to an arrangement of tread etc. However, all such similar successive groups elements thereon for the purpose of reducing are repeated so that the noises produced recur noises produced by such tires when in use regularly or periodically with resulting rythmical Broadly, the invention provides an arrangement pitch characteristics, either directly from the 5 of traction elements or blocks on tire treads in Vibrations or from beats due to wave interfersuch a manner that no successive similar groups ence. Accordingly, such successive similar groupof elements or blocks recur around the circumings are only slightly effective in the diminution ference of the tire. of noises.

1c The noises produced by vehicle tires, partic- The foregoing statment is rea ily understood lo ularly pneumatic tires, when in engagement with when certain mathematical values are considered.

a roadway are well known. Such noises origi- A 6.2516 tire driven at the rate of 30 miles per nate with the traction elements of the tread upon hour causes the freq ncy f impulses 0f t impact with the road surface. Such impacts set o p impeets to increase till a point Where a up definite noises which in pitch and degree are sound of definite pitch is produced. Such a tire 15 relatively dependent upon the length and/or size has a r umf r n e of app x at l 7 a d a of the traction elements, and the speed of rota- 30 miles per hour the tire moves horizontally at tion of the tire. An increase of the speed of 44' per second or 6.66 revolutions per second. If rotation of the tire produces a higher pitch. eight similar successive groups of traction ele- 20 A tire having a plain or rib tread is the most ments a e disp d in th tr h groups are 2 desirable so far as the noise characteristics are imp t d With gr d at the a e of 53 groups concerned as it produces a noise which is low per second. Each traction element or block proin degree and without pitch. However, it is pracduces a separate noise impulse during each rotatically necessary to provide tire treads with anti= tion of the wheel, and each group of traction eleskid elements. 'When the anti-skid configuraments likewise produces combined impulses. 5 tion is broken up into a number of circumfer- If the number of these impulses per second is entially spaced traction units the pitch noises in reas d, the con ry imp disappear produced depend upon the proportioning and the and a continuous note is heard when the impulses grouping of the traction elements. The more reach about p Second- AS e frequency 0 30 nearly continuous ribs are approached, as by the impulses is increased beyond this number the 30 providing long traction elements, the lower the p t h 01 th oise is a S Accordingly, such it noise in pitch, and conversely, the shorter tractread arrangement not only produces a hightion elements produce a pitch of higher frefrequency tone raised by the individual traction quency. elements, but also produces a low-frequency tone In general practice, a tread configuration comy es 0f t group impulses Which ed 35 prises a plurality of uniformly proportioned 30 per second at 30 miles per hour. traction elements spaced at regular distances cir- We propose to eliminate such low frequency cumferentially of the tire. Upon engagement tones by eliminating the use of similar successive with the ground these configurations produce gr ups of tractionelements, each similar succes- 40 a sound of definite pitch. In an efiort to avoid sive group having a plurality of separate traction 40 the uniformly proportioned traction elements, it e s of Va y g P D We Propose an has been proposed to separate them and interarrangement of traction elements in which nonpose traction elements of dilierent proportions uniform groups of traction elements of a given to form a contiguous row of traction elements e a e inte p sed W non-uniform E D 0f having a proportionate sequence in the order of traction elements of another size so as not to 45 A -B, etc. A tire tread having traction eleproduce similar successive groups of traction elements in such a sequence produces sounds in ments with their resultant periodical noises. which two or more tones are blended. In such This arrangement divides the circumference of a case, however, the frequency of the recurring the tire into arcs, each are having tread elenoise groups is so rapid that the total sound ments of a uniform size but of a different size 5 is not substantially reduced as they constitute from those of adja p and the angles in effect successive similar groups. Such arsubtended by the several arcs varying around the rangements have been enlarged by using other circumference of the tire. arrangements of similar successive groups of With this construction the traction elements traction elements as A-BCB-A-B--CB of one group produce a series of sound impulses 55 of similar characteristics but their number is so small that they do not produce a pitch sound. The second group produces dissimilar sound producing vibrations, while the subsequent groups of similar proportions vary in number of impulses so as to avoid a uniform repetition of sound.

The accompanying drawing illustrates a present preferred embodiment of our invention in which:

Fig. 1 is a side view of a tire showing a preferred embodiment of the' invention; and

Fig. 2 is a plan view of a portion of the tire tread.

Referring to the drawing. a tire tread embodying our invention is illustrated as having 56 traction elements or blocks A, B, C, disposed circumferentially of the tire. The arrangement illustrated in the direction of the count from the starting point of Fig. 1 is A-6B-A 5CA5B A-6CA7B'A-6C-A6B--A-'IC. The single blocks or elements A are of a size intermediate between the blocks B and C so as to provide a graduation in appearance between the groups of B and C elements.

As shown in Fig. 2, the blocks may be disposed in parallel series 2 and I of different shapes. A central rib 4 may be disposed between the series.

-Preferably the blocks in the rows 2 and 3 are staggered with respect to each other by substantially half a block or pitch length.

Numerical values for the blocks A, B, and C, in

the No. 2 rows of a 6.25-16 pneumatic tire are A==1.340"; 13:1.206"; and C=1.473". In the No. 3 rows,4:he'circumferential lengths may be varied as by using lengths E=1.366"; F=l.299"; G=1.503"; in the sequence E-6F-E5G E4FE-6G--E7FE-6GE6FE7G. The individual elements or blocks of the inner series No. 3 usually are made slightly longer than those of the outer series 2 because of the greater circumference of the tire near its center. These series are. preferably connected by-short rubber necks 8.

Referring to Fig. 1, the approximate arcs occupied by each of the groups, and allowing approximately 7 for each of the intermediate blocks A, beginning from the starting point are:

. Degrees 6B 36 5C 34 6C 41 7B--- 40 6C 41 6B 36 It is to be understood that the foregoing values and the specific groupings shown in the drawing are illustrative of only one specific form of the invention and that many other forms, proportions and arrangements of tread elements and/or blocks may be used within the spirit of the invention.

With the illustrated construction, a tire driven at an operating rated 30 miles per hour completes thetire cycle 6.66 times per second. Un-

. der these conditions no group of tread elements,

as shown in Fig. 1, can produce more than 13.32 group impulses per second. As it requires at least 30 impulses per second to produce a continuous note, the group arrangement of the present invention eliminates the low frequency tone raised by sound vibrations from traction elements arranged in similar successive groups.

The periodicity of uniform group impulses having been broken up, the next consideration is the characteristics of the noise producing vibrations raised by series of similar individual or a series of dissimilar individual traction elements. Sounds which have the same loudness and dominant pitch may differ in the complexity of the vibrations, and may, therefore, produce a very different effect on the ear. As-applied to a tire tread embodying the present invention, each individual traction element or block is capable of producing vibrations varying in degree and in accordance with the relative proportions of the traction element. However, such vibration of a single traction element is of short duration and does not reach the stage of a pure tone until repeated for a length of time exceeding the minimum required by the ear for tone perception. In the illustrated embodiment of ourinvention as many as seven equally spaced and proportioned blocks may be arranged in a single group, although the seven groups are interposed with other groupings. Such a group develops similar impulses of frequency capable of producing sound of definite pitch. However, the duration of the total group impulse is so short that the pitch raised is incapable of registration by a human ear. At 30 miles per hour a TC group produces noise for about .022 second, whereas theminimum time for tone perception is about three times this period.

While the traction elements could be designed or apportioned so that the successive elements each would be of different proportions and thereby eliminate entirely equal frequencies of impulses, there are practical reasons which justify the repetition of traction elements of similar proportions. Such tread elements should be held within definite circumferential lengths in order to retain their traction characteristics. Also there are advantages in machine operations in the manufacture of the molds in duplicating at least certain of the traction elements. Furthermore, as a matter of appearance, tread configurations of conventional designs should retain substantial uniformity. For this reason the intermediate blocks A are used.

Accordingly, we have provided a tire tread which diminishes audible noises of definite pitch to a degree not hitherto attained. Our circumferential arc arrangement of traction elements dispels fundamental vibrations and results in sound impulses being broken into a complexity of vibratory noises. The absence of a definite pitch permits the noise developing vibrations to neutralize or otherwise intermingle with each other so that a diminution of noise is effected. The ultimate result effected by our arrangement of tread elements is the production of subdued sound not displeasing in quality.

While we have shown and described a present preferred embodiment of the invention, it is to be understood that the invention may be otherwise embodied within the spirit of the invention and the scope of the appended claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A tire having a tire tread comprising a plurality of groups of tread elements arranged circumferentially of the tire, the tread elements in each group being of the same size and shape circumferentially of the tire but of a different size than those in adjacent groups and the number of elements of a given size varying between some of the groups thereof, whereby the circumference of the tire is divided into arcs of non-uniform lengths and aperiodicity is obtained in the sound resulting from engagement between the tread elements and a surface over which the tire travels.

2. A pneumatic tire having a tire tread comprising a plurality of parallel series of groups of tread blocks arranged circumferentially of the tire, the tread blocks in each group being of the same size and shape circumferentially of the tire but of a different size than those in adjacent groups and the number of blocks of a given size varying between some of the groups thereof, whereby the circumference of the tire is divided into arcs of non-uniform lengths and aperiodicity is obtained in the sound resulting from engagement between the tread blocks and a surface over which the tire travels.

3. A pneumatic tire having a tire tread comprising a plurality of groups of substantially rectangular tread blocks arranged circumferentially of the tire, the tread blocks in each group being of the samepsizeand shape circumferentially of the tire but of a different size than those in adjacent groups and the number of blocks of a given size varying between some of the groups thereof, whereby the circumference of the tire is divided into arcs of non-uniform lengths and aperiodicity is obtained in the sound resulting from engagement between the tread blocks and a surface over which the tire travels.

4. A tire having a tire tread comprising a plurality of groups of tread elements arranged circumferentially of the tire, the sizes of the elements in some of the groups being different from the sizes of the elements in another group and the circumferential lengths of some of the groups being different from'the lengths of some of the other groups whereby aperiodicity of sound is produced during movement of the tire. I

5. A pneumatic tire having a tire tread com prising a plurality of groups of tread blocks arranged circumferentially of the tire, the tread blocks in each group being of the same size and shape circumferentially of the tire but of a dif;- ferent size than those in adjacent groups and the number of blocks of a given size varying between some of the groups thereof, whereby the circumference of the tire is divided into arcs of non-uniform lengths and aperlodicity is obtained in the sound resulting from engagement between the tread blocks and a surface over which the tire travels, and a transition block of an intermediate size disposed circumferentially between adjacent groups whereby a gradual transition in appearance between the several groups of blocks is produced.

6. A pneumatic tire having a tiretread comprising eight groups vof tread blocks arranged circumferentially of the tire, the tread blocks in each group being of the same size and shape circumferentially of the tire but of a diiferent size than those of adjacent groups, the number of blocks in adjacent groups of a given size varying between some of the groups thereof, and a transition block of an intermediate size disposed circumferentially between each pair of groups, whereby the groups subtend angles at the centre of the tire varying from approximately 28 to 41 size disposed circumferentially between each pair of groups, whereby the groups subtend angles at the centre of the tire varying from approximately 28 to 41and aperiodicity in the sound produced by the tire is secured.-

8. A pneumatictire having a tire tread comprising eight groups of substantially rectangular tread blocks arranged circumferentially of the tire, the tread blocks in each group being of the same size and shape circumferentially of the tire but of a different size than those of adjacent groups, the number otblocks in adjacent groups ofagivensizevaryingbetweensomeofthe groups thereof, and a transition block of an intermediate size disposed circumf tiaily between each pair of groups, wh the groups subtend angles at the centre of the tire varying inthesoundproducedbythetireissecmed.

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